Occupationally-related low back disorders (LBDs) are the leading cause of lost work days and the most costly occupational safety and health problem facing industry today. Research concludes the biomechanical stability of the spine plays a significant role in low-back injury and prevention. Stability is achieved through a complex mechanical balance between external load and neuro- physiologic control factors including active muscle stiffness, reaction time and response amplitude. Personal factors such as gender and fatigue contribute to LBD risk because they influence neuromuscular response characteristics and associated stability. Unfortunately, existing analyses of spinal stability ignore the dynamic response characteristics of the neuromuscular system. To control LBD risk, to assure safer gender inclusion in the workplace, to facilitate work/rest and training schedules to prevent fatigue related injury prevention, and to improve clinical and rehabilitation assessment; it is necessary to quantify how neuromuscular response dynamics influence spinal stability. It is also necessary to understand how gender, fatigue and spinal posture influence these neuromuscular control factors and the associated risk of spinal instability. The goal of this research is to quantify dynamic stability of the spine and the influence of gender, fatigue, and spinal posture on musculoskeletal stability. Neuro- physiologic components of dynamic spinal stability, including truck stiffness, reaction time and response amplitude, will be measured form a sudden loading protocol and incorporated into a biomechanical model that will quantify dynamic spinal stability. Empirical measures of spinal stability will be recorded from potential energy protocols published from our laboratory. The experiments are designed to change spinal stability requirements without changing biomechanical equilibrium while observing trunk muscle coactivity associated with the recruitment of stability. These will provide empirical estimates of stability and be employed to validate the dynamic stability model. The influence of gender, fatigue and spinal posture on dynamic stability and neuromuscular response dynamics will be evaluated through each of these protocols. Research has established an epidemiologic link between neuromotor response behavior and LBD risk. The proposed effort represents the first to consider the biomechanics of dynamic neuromotor behavior in the control of spinal stability.